Halloween is observed in several countries on 31 October, the eve of the Western Christian feast of All Hallows' Day. (Photos: AP)

Boys, dressed as monsters, prepare to make the rounds of houses to solicit candies and sweets known as "Trick or Treat" in celebration Halloween.

One-year-olds Jaxon Creedy, left, and Aiobha Granger are photographed as they sit on a haystack during a visit to the National Botanic gardens' annual decorated pumpkin competition and exhibition, in Dublin, Ireland.

A visitor to a Halloween themed festival takes a selfie near decorations in Beijing, China.

Participants dressed in costumes celebrate Halloween in Lan Kwai Fong, a popular nightlife district in Hong Kong.

A local prepares his make up as he gets ready to participate in Halloween in Santiago, Chile.

Canadian Prime Minister Justin Trudeau walks with his son Hadrien as they go trick or treating at Rideau Hall on Halloween in Ottawa.

A father and son wearing Coco movie character Halloween costumes walk past the government palace where police stand guard in downtown Quito, Ecuador.

Television personality Padma Lakshmi attends Heidi Klum's 19th annual Halloween party at Lavo New York on Wednesday.

A reveler marches along Sixth Avenue during the Greenwich Village Halloween Parade.

Model and television personality Heidi Klum, right, and boyfriend Tom Kaulitz dressed as Shrek and Princess Fiona arrive at her 19th annual Halloween party at Lavo New York.